Okay, well that output shows 4 device nodes present. How many CD/DVD drive units do you actually have connected? Other hardware devices can present these as well. (For example, some USB storage hardware present themselves as SCSI CDROM devices).

Now, when you have your docking station attached, what software are you running that does not recognise your 'docking station' DVD unit? It might be more a case of tweaking udev to symlink /dev/dvd with the preferred drive to for example.

Theres no additional drives attached or any other things like external mice pen drives etc but I suppose it is possible something like the touchpad or the mouse pointer in the middle of the keyb could be seen as a device.

I checked in /etc/udev/rules.d but 70-persistent-cd.rules isnt in there. Reading about UDEV I see mention that it should automatically create this file at bootup but it can be generated by hand. However Im now not sure if it should be generating but isnt for some reason and if I do go to create it myself what has to go into it.